The present invention generally relates to an electrical wafer or circuit board configured for use within an electrical connector, and more particularly to an electrical wafer having at least one split ground plane.
In the past, controlled impedance connectors have been proposed that are used as board-to-board connectors. Many connectors house a plurality of circuit boards, or electrical wafers, having edges that mate with edges of corresponding contacts in an adjoining connector. The connectors may electrically connect components, such as motherboards and daughterboards.
FIG. 7 is a cross-sectional view of a portion of a conventional electrical wafer 100. The electrical wafer 100 includes a main body 112 formed of a dielectric material, such as molded plastic. Signal tracks 114 are positioned on one side 102 of the electrical wafer 114 and may be separated from one another by a gap. The second side of the electrical wafer 104 includes at least one ground plane 116. As shown in FIG. 7, the ground plane 116 is shared by both signal tracks 114. Thus, electrical energy may travel from a first signal track to the ground plane 116 and into the second signal tracks (as shown by the arrows).
Examples of electrical connectors that utilize wafers are disclosed in United States Patent Application Publication US 2002/0009926 A1, filed Feb. 3, 2000 and published Jan. 24, 2002 (xe2x80x9cthe ""926 applicationxe2x80x9d). The ""926 application is incorporated by reference herein in its entirety. The ""926 application discloses an electrical connector that includes a housing that carries a plurality of wafers or circuit boards. FIG. 9 illustrates an electrical connector 1111 according to the ""926 application. As shown in FIG. 9 (FIG. 1 of the ""926 application), the electrical connector 1111 includes a housing 1112 having a front housing 1120 and an organizer 1130. Wafers 1113 having mating edges 1116 are received and retained within the housing 1112. The wafers 1113 extend parallel to each other in a spaced-apart relationship. The wafers 1113 include signal tracks that provide electrical paths through the connector. Each electrical path extends from a mating interface at one end of the connector to a mounting interface at another end of the connector.
The signal tracks of the wafers are separated by common ground planes. Ground planes may be provided on both sides of the wafer. At least a portion of the ground plane on one side of the wafer is located directly opposite a signal track on the opposite side of the wafer. Therefore, two signal tracks on a first side of the electrical wafer have a common return path to a ground plane, while a signal track on the second side of the wafer is directly across from the same ground plane through the main body of the wafer. The body of the wafer is typically a thin layer of dielectric material. Additionally, the signal track on the second side of the electrical wafer is typically separated from other signal tracks on the second side of the wafer by separate ground planes.
Electrical noise, jitter and the like generated by one signal track, or signal route, may pass into the ground plane. While the ground plane absorbs and alleviates noise and jitter, the ground plane may not entirely remove the noise and jitter. Hence, the ground plane may permit a small portion of the electrical noise, jitter and the like to pass from one signal track to another signal track. That is, the ground plane may couple with one signal track and act as an electrical conduit to another signal track, thereby allowing electrical noise and jitter to pass from one signal track to another signal track. Consequently, the signal tracks that share the same ground planes may still experience noise, jitter and the like thereby degrading performance within the electrical connector.
FIG. 8 is a cross-sectional view of a portion of another conventional electrical wafer 118. The electrical wafer 118 includes differential signal pairs 120 that each share a common ground plane 122. Thus, electrical energy may travel from one differential signal pair 120 to another differential signal pair through the common ground plane 122.
Many connector systems are arranged to convey signals arranged in differential pairs. Each differential pair includes complimentary signals such that if one signal in a differential pair switches from a zero logic state to a one logic state, the other signal in the differential pair switches from a one logic state to a zero logic state. If the differential pair signals are skewed in time with respect to one another, or if the transmission line characteristics of the signal tracks in a differential pair differ, cancellation between signals of the differential pair does not occur and a new current (resulting from the fact that the signals did not cancel) may be generated and passed to the ground plane. This new current is passed from one differential pair to another differential pair through the common ground plane, thereby causing interference and degrading performance within the connector.
Thus, a need exists for an electrical wafer that minimizes the effects of adjacent signal paths communicating with one another. Further, a need exists for an electrical wafer that exhibits less interference, cross-talk, jitter and the like.
Certain embodiments of the present invention provide an electrical wafer configured to be housed within an electrical connector, comprising a main body and a plurality of signal routes and ground planes. The main body is formed of a dielectric material having first and second sides. The plurality of signal routes are positioned on a first side of the main body. Each of the signal routes comprises a signal contact pad at a mating edge of the electrical wafer, a signal terminal at a mounting edge of the electrical wafer, and a trace connecting the signal contact pad with the signal terminal. The plurality of ground planes positioned on the second side of the main body are positioned such that each of the ground planes is directly across from one of the plurality of signal routes located on the first side of the main body. Neighboring ground planes on the second side are separated by a ground-to-ground gap.
Certain embodiments of the present invention also provide an electrical wafer configured to be housed within an electrical connector comprising a main body, and a plurality of signal routes, gap routes and ground planes. The plurality of signal routes, gap routes and ground planes are positioned on each of the first and second sides of the main body. Each of the plurality of signal routes on one of the sides is located between two of the plurality of ground planes on the same side of the main body. Each of the ground planes on one side of the main body is positioned between one of the plurality of signal routes and one of the plurality of the gap routes on the same side of the main body.